Carpets having a cut-pile construction are typically used in residences, while loop-pile carpets are commonly used in commercial buildings. Carpet yarns suitable for making cut-pile and loop pile carpets are referred to as bulked continuous filament (BCF) yarns or staple spun yarns. These yarns are generally subjected to certain processing steps, such as twisting, before they are used in carpets.
In the past, BCF yarns were ring-twisted in a two-step process using ring twisters. In the first step, singles twist was imparted into each component yarn. The singles twist could be in the "S-twist direction" or the "Z-twist direction". By "S-twist direction", it is meant that when the yarn is held vertically, the spirals around its central axis slope in the same direction as the middle portion of the letter, "S". By "Z-twist direction", it is meant that when the yarn is held vertically, the spirals around its central axis slope in the same direction as the middle portion of the letter, "Z". The singles-twist component yarns were then plied together in the opposite direction of the singles twist by an equal number of turns per inch (tpi), and the singles twist was effectively removed to form a ring-twisted structure.
Today, the majority of BCF yarns are twisted in a one-step process using a cable twister. The same twisting operation as described above with the ring twisters is performed on cable twisters, except the process is done in a single step at high speeds and produces large packages suitable for subsequent heat-setting. Common cable-twister machines include the Verdol (France), Volkmann (Germany) and Muschamp (England). Generally, these cable twisters operate by feeding one component singles yarn from a yarn package located on a creel and a second component singles yarn from a yarn package located in a yarn supply bucket. The creel yarn is fed through a spinning disc and emerges to form a ballooning creel yarn. The bucket yarn is fed through a tensioner to a guide, where the creel yarn from the balloon wraps around the bucket yarn to form a cable-twisted yarn structure. This cable-twisted structure is also referred to as a two-ply cable-twisted structure, because it comprises a singles creel yarn ply-twisted with a singles bucket yarn.
In order to make a three-ply cable-twisted structure, two singles yarns are first cable-twisted together. This two-ply cable-twisted yarn is then cable-twisted with a singles yarn to produce a three-ply cable-twisted structure. Likewise, in order to make a four-ply cable-twisted structure, two singles yarns are first cable-twisted together to make one component yarn. Two different singles yarns are cable-twisted together to make a second component yarn. The first component yarn is then cable-twisted with the second component yarn to make a four-ply cable-twisted structure. These methods can also be used to make five-ply, six-ply, etc. cable-twisted structures. However, one problem with using this method to make cable-twisted yarn structures is that it involves multiple cable-twisting steps. For instance, three cable-twisting steps are necessary to make a four-ply cable-twisted yarn. Singles yarns A and B must be cable-twisted to make component yarn 1 and singles yarns C and D must be cable-twisted to make component yarn 2. Component yarns 1 and 2 are then cable-twisted to make the four-ply structure. This process is costly and time consuming due to the multiple cable-twisting steps involved. Further, the resulting yarns have a highly cabled structure.
The present invention provides a new cable-twisting process which does not involve multiple cable-twisting steps. When singles yarns of different colors are used in this process, the resulting cable-twisted multi-colored yarn exhibits an attractive color popping effect, wherein the different colors of the singles yarns are separated from each other and have good vividness.